1) Field of the Invention
The present disclosure relates to rubber compositions comprising unsaturated organic polymers, fillers and silane. The present disclosure also provides for a process of making said rubber composition as well as articles made therefrom.
2) Description of Related Art
The use of the silica/silane-filler system to reduce the rolling resistance and improve the wet traction of passenger car tires is well known in the art. A reduction of rolling resistance and therefore less fuel consumption are also of strong interest for truck tires. However, the use of silica to replace carbon black filler in natural rubber (NR) containing formulations, such as truck tread compounds, is limited, due to the poor abrasion resistance. At the present time, truck tire treads use highly reinforcing carbon black for maximum reinforcement and excellent resistance to abrasion. The replacement of carbon black by silica in truck applications has been hampered by ineffective coupling of the silica to the polymer chains of natural rubber.
The polysulfurized alkoxysilanes, such as bis(triethoxysilylpropyl)tetrasulfite (TESPT), and blocked mercapto-functional silanes such as 3-octanoylthio-1-propyltriethoxysilane, are currently regarded as the most effective and the most widely used coupling agents in rubber compositions for tires, especially those compositions containing styrene-butadiene rubber or butadiene rubber. The reinforcing efficiency and abrasion resistance of vulcanizates filled with silica are not good enough to justify the replacement of carbon black in formulations containing high levels of natural rubber.
The use of non-sulfur silanes is focused on the use of activated double bonds to improve the coupling between fillers and polymer, notably natural rubber. But these non-sulfur coupling agents have shown inadequate coupling performances or performances inferior to those offered by polysulfurized silanes such as bis(triethoxysilylpropyl)tetrasulfide. In addition, the known non-sulfur silanes are very reactive with conventional fillers and elastomers and are therefore difficult to use. When known non-sulfur silanes are used at levels necessary to achieve optimum coupling of filler to the host elastomer, the uncured filled elastomer typically exhibits poorly dispersed filler and short scorch times during curing. Both good filler dispersion and good filler reinforcing efficiency are required to achieve satisfactory end-use properties.
It would be desirable for various rubber applications to have a rubber composition that utilizes increased levels of silica and lower levels of carbon black while still exhibiting the properties of low scorch, good filler dispersion and improved abrasion resistance.